During the installation of and interconnection of various equipments in telephone central offices, it is necessary to make frequent wiring checks as to the integrity of connections made by means of exchange cable which is utilized to interconnect the various equipments. In many instances partially connectorized cable is utilized; that is, a cable having a number of wires that are connected at first ends to a plug-like connector and at the other or second ends are connected by wire wraps to terminals on a frame or in another piece of equipment. The pre-connectorization of the cable is usually accomplished in a cable manufacturing factory or at a distribution center before shipment to the telephone exchange. Prior to cutover of newly installed equipment connected to the central office equipment by connectorized cable, it is necessary that the cable be checked for proper connection of the plug terminals to the switch frame or distributing frame terminals.
A number of test facilities have been developed for making a number of checks of connectorized cable so as to ascertain shorts, continuity and proper wire interconnection. One such test facilities is shown in U.S. Pat. No. 3,492,571 to D. A. Desler assigned to the Western Electric Co., Inc., where a multi-conductor cable having plugs at opposite ends is checked for shorts, opens and wires that are misconnected or cross-connected between terminals at the respective plug ends of the cable. This test facility includes means for sequentially applying test pulses to terminals at one plug end and sensing the receipt of the signals at the second plug end. The received signals are then compared with signals generated by a reference program circuit. The signals from the plug end of the wire and the reference circuit are applied to a comparison circuit to determine correctness, and if the signals do not properly compare then error signals are generated. The error signals are utilized to operate visual displays that provide information as to the faulty wires and the type of error determined by the comparison circuit.
There is a need for a lightweight, portable test facility for checking cable wiring in a telephone exchange that can be transported, set up and run by a single operator. In use a telephone central office such a test facility should be able to test for shorts between cable wires, open wires and misconnected or cross-connected wires, and this test facility should also have the capability of testing for shorts to a distributing or other switch frame to which the non-connectorized ends of the cable wires are connected. In addition, the test facility should have the ability to detect shorts between the switch frame terminal connected wires and the power source wiring for the equipment mounted on the frame.
Such a test facility should also possess the ability to rapidly perform the test without the utilization of relays, mechanical stepping switches or other bulky or slow operating components. Where the connectorized cable wires to be tested is terminated at first ends to a plug and at other ends to the terminals mounted on a chassis or frame, such as a telephone office distributing frame, the test facility should also include means for sequentially applying test pulses through a plug end of the cable to the frame mounted terminals without actually wiring the test set to the terminals on the frame. It would also be desirable if the test facility provided visual fault displays, both at the plug end of the cable as well as at the site where the cable wires are connected to the terminals on the switch frame. The test facility of the present invention obtains the desirable criteria set forth above.